Time Warner posted strong fourth quarter earnings on Wednesday as the company capitalized on the continued success of Harry Potter and the Deathly Hallows Part 1, growth in networks stemming from advertising and subscription growth in HBO and TVS, and improved productivity in its publishing unit, Time Inc. The company thus decided to revamp its share buyback program and hike its quarterly dividend, to the joy of investors who propped the stock up more than 7% in early trading.